One thing that is sure to make my wife roll her eyes in disgust is when we're out somewhere and I check in to a venue using Foursquare. I enjoy using the Foursquare iPhone app to check in, gain or lose the mayorship of a location and occasionally get one of those cool badges that they award to users (I'm particularly proud of my Jobs, I'm on a boat! and JetSetter badges).
The free app has just been updated and now adds two fun features -- adding photos and comments to check-ins. This is handy, since I currently have to use multiple apps to a) check in and b) send photos of delicious food to friends. Now it's all possible in one app. There's also a history page on the Foursquare website where you can see all of the places that you've visited.
Comments are only viewable by your Foursquare friends, but photos that you add are added to a venue and can be seen by anyone. Considering that many iPhone users do this all with a mashup of Twitter clients, photo apps and Foursquare or Facebook, the Foursquare update is a welcome surprise.
In the update notes (at right), Foursquare mentions that they're up to 5 million users. Congratulations, and thanks for the Christmas gift.